30 day lease termination

[D'Juan Thurmond]

What up BP!  I just purchased a house hack duplex in Upstate SC.  I currently have both units occupied and they are on month to month leases.  I sent out a 30 day notice to the unit I decided to reside in.  The tenant decides to move out in the middle of the month.   When I prorate the tenant last months rent do I prorate it for the 30 days or til the day she moves out which in this case is the 15th of the month?  

Thanks in advance!